In his first public response, Lula said he was ready to cooperate with prosecutors because he had committed no crime and called charges against him "pure fiction" aimed at stopping him from running for office again.

Counting the Cost - Brazil: Petrobras and the cost of corruption

Lula is specifically accused of benefiting from renovations at a beachfront apartment in the coastal city of Guaruja in Sao Paulo state. The improvements, valued at about $750,000, were made by construction company OAS, one of those involved in the kickback scheme emanating from Petrobras.

Prosecutors also believe Lula benefited from OAS paying the rent on a storage unit to house gifts that he received while president.

Lula says he visited the penthouse apartment but never owned it.

Brazil's president between 2003 and 2010, Lula left office with an approval ratings of more than 80 percent.

However, the Petrobras scandal, recession in Latin America's largest economy and political turmoil in recent years have hurt his reputation.

Lula's hand-picked successor, Dilma Rousseff, was removed from office by the Senate last month for illegally shifting funds between budgets. Rousseff and Lula have argued that the impeachment push was also politically motivated, a way to weaken their Workers' Party.

The next step will be for Sergio Moro, the judge overseeing the probe, to decide whether Lula will stand trial.